Intellectual disability refers to challenges or limitations in cognition, learning, communication, and adaptive behaviour that are manifested before the age of 18. Though the term itself was not used during the eugenics movement, the very idea of intellectual disability was an organizing principle of eugenics, as it represented a form of deficiency that this movement was trying to eliminate, treat, manage, and prevent. There have been significant shifts and debates regarding terminology since then, and in the last twenty years “intellectual disability” has come to replace older terms like mental retardation, mental deficiency, and feeblemindedness. Today, there are both medical and functional classifications of intellectual disabilities. Within the medical model, intellectual disability is viewed as a pathological state based upon a concept of normal intelligence (and IQ score), while functional classifications focus on the individual’s adaptive skills and need for social supports within his or her environment. However, intellectual disability remains a contested term by many disability theorists, advocates and self-advocates who challenge these classificatory systems and argue that it is a socially constructed concept with a pernicious history. Though significant changes have improved the lives of people labelled “intellectually disabled,” new reproductive technologies aimed at eliminating forms of intellectual disability and the prospect of enhancing cognitive abilities suggest that a new form of eugenics may be on the horizon.

Sub-categories
In tracing the history of this classification, one finds many sub-categories within the broader designation of intellectual disability. During the eugenics movement, “feeble-mindedness” was used as a broad term, within which were categories of mental deficiency in ascending order of mental ability: idiot, imbeciles, moral imbeciles, and morons. In the late nineteenth century these distinct types were defined based on physical, psychological and behavioral criteria, and often overlapped with other conditions (e.g. insanity, epilepsy, Down syndrome). With the arrival of intelligence tests in the early twentieth century, eugenicists were able to more precisely demarcate these sub-categories and expand the campaign to identify, treat, segregate, and in many cases sterilize individuals deemed feeble-minded. Shifts in terminology throughout the twentieth century, thanks in large part to the efforts of parents, self-advocates and disability rights activists, reflect broader changes in the way intellectual disability has been understood. Intellectual disability is still classified according to degrees of severity (mild, moderate, severe and profound), and it is associated with a broad range of etiologies and medical conditions. However, there are also sub-divisions based on intellectual function and adaptive behaviours that include conceptual, social, and practical skills (AAIDD).

Causes of Intellectual Disability
There are many different conditions associated with intellectual disability, and multiple causes have been identified, ranging from genetic explanations to environmental and social causes. In the early twentieth century, the view that intellectual disability was a heritable trait was at the core of many eugenic theories and practices. In Heredity in Relation to Eugenics, Charles Davenport identified two laws of inheritance of mental ability: “Two mentally defective parents will produce only mentally defective offspring” and “Aside from ‘mongolians’ probably no imbecile is born except of parents who, if not mentally defective themselves, both carry mental defect in their germ plasm.” It was this belief in the hereditary nature of mental ability that justified many of the eugenic programs that were put into place to prevent the spread of feeble-mindedness, most notably sexual segregation in institutions and involuntary sterilization. While hereditarian theories of intellectual disability like Davenport’s have been scientifically discredited, contemporary research into the genetic basis for certain kinds conditions associated with intellectual disability has raised the spectre of heredity and disability once again.

Beyond heredity, there were other causes named that further fuelled both negative and positive eugenic programs to ensure fitness of future generations. The belief that idiocy could be avoided by proper reproductive practices was promoted in public health literature and popular media. At the same time, associations were drawn between intellectual disability and alcoholism, pauperism and criminality. Though they were not always scientifically proven etiologies, these causal connections held sway in eugenic arguments regarding the treatment of people with intellectual disabilities.

Today, a number of causes of intellectual disability have been identified, including genetic, neurobiological and environmental factors. Etiologic classifications also focus on the timing of the causative event(s): prenatal, perinatal, or postnatal (Harris, 135). There are now more than 750 genetic disorders associated with intellectual disability (e.g. Trisomy 21, Fragile X syndrome). Pre- and perinatal causes include infections, exposure to toxins, and trauma during delivery. There are also numerous external factors (e.g. environmental toxins, malnutrition) that are considered causes of intellectual disability postnatally. Researchers and critical disability theorists have also investigated how socioeconomic disadvantage, race, and ethnicity contribute to the likelihood of being labelled “intellectually disabled,” suggesting that there are complex social mechanisms through which intellectual disability is constructed and produced.

Characterizations of the “intellectually disabled” during the eugenics movement
In addition to the scientific classifications and etiologies that defined intellectual disability, there were many images, concepts, and judgments associated with “the intellectually disabled” during the eugenics movement. Physically, they were often defined in animalistic and racist terms (e.g. mongoloid, monkeyish, deformed). Many were also considered subhuman by virtue of these physical features and the fact that they lacked reason. Behaviorally, they were defined as immoral, depraved, degenerate, and a menace to the broader population. At the same time, however, some “idiots” were viewed as innocent and vulnerable, and in need of protection from society because of their intellectual disabilities. Some were considered to be educable, while others were believed to be in a hopeless, arrested state of development. Yet two fundamental assumptions permeated all of these designations: people with intellectual disabilities were fundamentally unfit, and intellectual disability as a condition was objectively abnormal and undesirable.

The attribution of mental inferiority to multiple groups was another key feature of the eugenics movement. Thus, while eugenicists focused on conditions that remain associated with intellectual disability today (e.g. Down syndrome), they also labelled other individuals as intellectually disabled because of their membership in certain racial, ethnic or socially undesirable groups. This included many immigrant groups, aboriginal and indigenous peoples, criminals, alcoholics, paupers, prostitutes, and women who had given birth to illegitimate children. This shows how permeable the boundaries of this category were, and how the suspicion of intellectual disability justified many of the eugenic programs that targeted populations who were not in fact disabled.

Institutionalization
The history of intellectual disability can also be traced through the institutions that housed bearers of this label. In the mid-nineteenth to early twentieth century, the belief in the educability and vulnerability of many “idiots” and “feeble-minded” led to the construction of training and residential schools for the feebleminded. However, as the eugenics movement gained traction and this population became increasingly viewed as a menace, many of these facilities became overcrowded custodial warehouses with no therapeutic or pedagogical aims. The institution became a site of incarceration, wherein human experimentation, involuntary sterilizations and other forms of physical and psychological abuse took place.

Intellectual Disability and the Legacy of Eugenics
As a response to the horrors of the eugenics movement, people with intellectual disabilities, their families and advocates, and many professional groups have worked toward a number of goals to achieve justice for people with intellectual disabilities and those who were wrongly labelled as such. The deinstitutionalization movement highlighted the severe abuses within institutions, and aimed at integrating individuals with intellectual disabilities into the community. Efforts to establish safe and humane residential settings where people with intellectual disabilities can flourish as full members of society continue today.

On the legal front, there have been numerous cases investigating the deplorable conditions in institutions for the “intellectually disabled” across Canada, and battles to get recognition and compensation for victims of involuntary sterilization. These efforts are part of a larger disability rights campaign to redress the abuses and violations perpetuated during the eugenics movement, and to assert the rights and dignity of people with intellectual disabilities. Strong advocacy and self-advocacy movements continue to combat the subhumanization, marginalization and devaluation of people with intellectual disabilities. Projects that give voice to individuals who have been silenced are an equally important step toward justice for people with intellectual disabilities.

In addition to critiquing models of intellectual disability that reify the concept of intelligence and pathologize different ways of knowing and being in the world, some disability theorists and bioethicists are raising concerns about the implications technological advances may have for people labelled “intellectually disabled.” The widespread use of prenatal screening and selective abortion targeting conditions like Down Syndrome, research into newer forms reproductive technologies and cognitive enhancements, and the defense by some bioethicists of a new “liberal eugenics” point to a resurgence of eugenic ideals aimed at preventing intellectual disability. How these technologies differ from past eugenic practices and what place intellectual disability will occupy in their justification and implementation remains to be seen.

-Licia Carlson

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